Ford 2003 Mustang Workshop Manual page 1536

10. CAUTION: Make sure the tool is seated correctly on the valve spring. Apply a small
amount of air at a time. This will prevent the tool from shifting and causing damage to
the cylinder head.
Install the air-operated spring compressor on the cylinder head.
11. Compress the valve spring compressor and remove the key from the valves.
12. Remove the intake valves and the valve springs.
1. Release the pressure and remove the valve spring compressor.
2. Remove the intake valves and the valve springs from the cylinder head.